Waking up with a painful sore on the inside of your cheek is confusing because the injury occurs without conscious awareness. This involuntary nighttime habit, known as nocturnal cheek biting, is a form of oral self-trauma. When chronic, the condition is medically termed morsicatio buccarum, resulting in thickened, whitish patches of the buccal mucosa (the lining of the cheek). Though unintentional, this biting signals that specific mechanical or physiological factors are active while you sleep.
Common Physical Causes of Nocturnal Biting
The primary mechanical reason for nocturnal cheek biting is involuntary jaw movement during sleep. The most common cause is sleep bruxism, a movement disorder characterized by clenching or grinding the teeth. These forceful jaw movements can pull the soft cheek tissue powerfully between the teeth, causing injury. Bruxism is often linked to stress, anxiety, or other sleep disturbances that increase the frequency of jaw activity overnight.
The anatomical structure of the mouth, specifically how the upper and lower teeth meet, also plays a role. Dental malocclusion (an improper bite or misaligned teeth) can create sharp edges or narrow spaces where the cheek tissue is easily caught. If teeth do not align correctly, cheek lining can be repeatedly trapped in the same spot during jaw movements, a vulnerability heightened during sleep.
Sleeping posture can also contribute to the problem. Sleeping on your stomach or side puts external pressure on the jaw, pushing the soft cheek tissue inward. This pressure forces the buccal mucosa closer to the occlusal plane (where the teeth meet), making it more susceptible to being bitten during a jaw clench. The resulting injury often creates swelling, which makes the area more likely to be bitten again, creating a cycle of trauma.
Professional Solutions and Diagnosis
Since nocturnal cheek biting is often a symptom of an underlying mechanical issue, consulting a dental professional is the most effective next step. Dentists perform a thorough examination to check for signs of sleep bruxism, such as excessive tooth wear, enlarged jaw muscles, or chronic irritation along the cheek’s biting line. They also assess bite alignment to determine if malocclusion is creating a vulnerable path for the cheek tissue.
The most common professional intervention is a custom-fitted nightguard or oral splint. This device is fabricated from a mold of your teeth and provides a physical barrier between the upper and lower teeth, protecting the soft cheek tissue. Unlike over-the-counter versions, a custom guard ensures a precise fit that stabilizes the jaw and prevents the trapping of the cheek.
For cases involving severe dental misalignment, the long-term solution may involve orthodontic treatment. Correcting the positioning of the teeth through braces or aligners can eliminate the specific points in the mouth where the cheek tissue is consistently vulnerable to trauma. If a dentist suspects the bruxism is severe or linked to a more complex issue, like obstructive sleep apnea, they may recommend a referral to a sleep medicine specialist for a comprehensive sleep study.
Immediate Actions to Manage the Problem
While seeking a professional diagnosis, you can take immediate steps to manage painful sores and reduce the likelihood of repeated injury. To promote healing, rinse your mouth several times a day with a warm saltwater solution (about half a teaspoon of non-iodized salt mixed into one cup of warm water). This rinse helps keep the wound clean and minimizes the risk of infection.
For existing sores, topical oral antiseptic gels can be applied to temporarily relieve pain and create a protective layer over the raw tissue. You should avoid eating highly acidic, spicy, or crunchy foods, as these will irritate the wound and slow down the healing process. Sticking to a diet of soft, bland foods for a few days can give the delicate cheek lining time to recover.
Behavioral adjustments, such as facial and jaw massage before bed, can help relax the muscles that contribute to nocturnal clenching and tension. Stress reduction techniques, like deep breathing or meditation, are also beneficial because they help manage the anxiety that often fuels bruxism. When sleeping, try to maintain a position on your back, which can reduce external pressure on the jaw that might otherwise push the cheek inward toward the teeth.